I have a quad monitor system with 2 nvidia cards. Twinview does not work. That is you cannot move windows between monitors in 2 video cards system. When I use xinerama with Separate X screen. (using Unity 2d or Kde, I do not expect much from Unity 3d or gnome 3). I get the four displays. The mouse can move between the displays. But when I click the menu button or and application on the launch menu nothing happens. No window is created.

I have not tested with KDE, but I have done testing of system setups like this with 3 monitors.

Gnome3 is the base for Unity2d, and Gnome3 as far as I have been able to find does not work with 3 or more monitors.

You will either have to drop back to Gnome2, and accept that you run a very none standard Ubuntu, revert to a previous version of Ubuntu based on Gnome2 or as I did, switch to XFCE works just great.

I am not even talking about unity or genome 3. They have multiple issues when it comes to more than 1 monitor.

The issue that I have is with kde. I cannot create a window or look at the main menu. I get no response. When I click on the corresponding icons. I want to remind you that I have two cards. May be the driver for the GT 550ti is not mature? Thanks

I would suggest you install XFCE and see if the problem persists in that enviroment, i'ts very simple on ubuntu

Code:

sudo apt-get update && sudo apt-get install xubuntu-desktop

Then logout
Under the cog wheel icon, select "XFCE"
Login

If everything now works as expected, you can eliminate

1. the nvidia driver
2. X

Leaving KDE at fault

If everything doesn't work, you should experiment with some more xorg.conf setups to see if you can make it work, if you cannot make it work at all, then it would seem there would be a fault either with X or the nvidia driver.

My own personal experience, acknowledging that I have NOT tested with KDE myself, is that the fault lay with the desktop environment (i.e. KDE/Gnome3 which as I said, underlies Unity2d).

I would suggest you install XFCE and see if the problem persists in that enviroment, i'ts very simple on ubuntu

Code:

sudo apt-get update && sudo apt-get install xubuntu-desktop

Then logout
Under the cog wheel icon, select "XFCE"
Login

If everything now works as expected, you can eliminate

1. the nvidia driver
2. X

Leaving KDE at fault

If everything doesn't work, you should experiment with some more xorg.conf setups to see if you can make it work, if you cannot make it work at all, then it would seem there would be a fault either with X or the nvidia driver.

My own personal experience, acknowledging that I have NOT tested with KDE myself, is that the fault lay with the desktop environment (i.e. KDE/Gnome3 which as I said, underlies Unity2d).

I had similar issues with XFCE, In fact with xfce the behavior was the worst. The desktop was not properly presented. On he other hand when I tried using window maker. It seems to work fine. Although all the monitors had display :0.0 (instead of :0.0 - : 0.3). I still think that the issue is incompatibility of the cards/nvidia driver and X.